The present invention relates to a fuel injector for an internal combustion engine that is provided with an in-cylinder fuel injection valve and an intake port fuel injection valve.
A fuel injector including an in-cylinder fuel injection valve, which directly injects fuel into a combustion chamber, and an intake port fuel injection valve, which injects fuel into an intake port, is known in the prior art. The fuel injector is switched between an in-cylinder injection mode and an intake port injection mode in accordance with driving conditions (refer to Japanese Laid-Open Patent Publication No. 7-103048).
The in-cylinder fuel injection valve injects high pressure fuel supplied from a high pressure pump. The high pressure pump pressurizes fuel with a plunger, which is reciprocated in cooperation with the rotational motion produced by the engine, to supply the high pressure fuel to the in-cylinder fuel injection valve. When intake port injection is performed, in-cylinder injection is stopped. However, the plunger continues to reciprocate in cooperation with the rotational motion produced by the engine. In this case, the reciprocation of the plunger repetitively draws low pressure fuel in and out of the high pressure pump.
The pressure of the low pressure fuel in a low pressure fuel pipe pulsates when the low pressure fuel is repetitively drawn in and out of the high pressure pump. The pulsation of the fuel pressure leads to differences in the amount of fuel injected into each cylinder. More specifically, in a cylinder in which fuel is injected into the corresponding intake port at a timing when the fuel pressure becomes high due to pulsation, compared to a cylinder in which fuel is injected into the corresponding intake port at a timing when the fuel pressure becomes low, a relatively large amount of fuel is injected into the intake port even if the fuel injection time length is the same.